IV93536: JAVA JIT: CRASH WHEN USING THE BALANCED GC POLICY ON POWER CPUS

APAR status

• Closed as program error.

Error description

• Error Message: SIGSEGV executing inside JIT compiled code is the
  most likely result of this problem, but other symptoms like a
  crash in the GC or the VM is also possible.
  .
  Stack Trace: The stack trace will likely be different for
  difference instances of the problem.
  .
  The problem can only occur on POWER machines (AIX and Linux PPC)
  and can only happen when running the 64bit version of the JVM.
  The problem was fixed in Java 6.0, 6.1 and 7.0, but we suspect
  that the issue is only possible when using the balanced GC
  policy which was introduced in Java 7.1.
  

Local fix

• The problem should be avoidable by not using the Balanced GC
  policy). i.e. remove the Java command line option
  "-Xgcpolicy:balanced".
  

Problem summary

• The JIT would incorrectly spill a register using 32bit
  store/load instructions in a rare case late in the code
  generation stage after determining that a load offset is large
  enough to require the use of a temporary register.
  

Problem conclusion

• The JIT was modified so that it generates 64bit store/load
  instructions for the rare path register spill when running a
  64bit JVM.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels

• R130 PSY

     UP

• R260 PSY

     UP

• R600 PSY

     UP